Japan on Monday summoned Russia’s ambassador to protest against a visit by Dmitry Medvedev, Russian president, to a disputed group of islands seized by Moscow during the second world war.Mr Medvedev’s three-and-a-half hour visit to the islands, known in Japan as the Northern Territories and to Russia as the Southern Kuriles, was the first by a Russian or Soviet head of state and threatens to reignite a bitter diplomatic feud over their ownership.It came as Tokyo is struggling to ease territorial frictions over a group of Japanese-controlled but Chinese-claimed islands in the East China Sea, a dispute that has rocked relations with Beijing and overshadowed a gathering of regional leaders in Hanoi last week.Seiji Maehara, Japan’s foreign minister, summoned Russian ambassador Mikhail Bely to protest at Mr Medvedev’s visit to the islands, which he said would “hurt the feelings” of Japanese citizens.“We’ve taken the consistent position that this is our nation’s territory, so the president’s visit to the area is very regrettable,” Naoto Kan, prime minister, told a session of Japan’s Diet.Japanese state broadcaster NHK quoted Mr Bely that Mr Medvedev’s trip was an “purely domestic matter” and calling for Tokyo to respond “calmly”.The visit, made despite warnings from Tokyo that it could “severely harm” relations, adds a new element of territorial sensitivity to Japan’s preparations for hosting a summit of the Asian Pacific Economic Cooperation nations in the eastern port city of Yokohama this month.Sino-Japanese relations have been chilled by a dispute sparked by the detention of a Chinese fishing boat captain following a clash with Japanese coast guard vessels near the Senkaku islands in the East China Sea last month.Despite the release of the captain, continuing frictions over the islands, known in China as the Diaoyu group, prompted Beijing to scrap at the last moment a planned summit meeting between Mr Kan and Chinese Premier Wen Jiabao in Hanoi on Friday.Some Japanese officials are concerned diplomatic tensions could also overshadow the Apec summit in Yokohama on November 13-14. Mr Medvedev’s visit also highlights the failure of Moscow and Tokyo to find a way to resolve their dispute over the ownership of the territories just north of Japan’s main island of Hokkaido.Last year, Mr Medvedev and then Japanese prime minister Taro Aso agreed to adopt an “outside the box” approach to resolve the issue, which has prevented them from signing a peace treaty formally to end second world war hostilities.However, the accord has sparked no obvious new thinking, with neither side offering potential solutions. Moscow has in the past suggested that it might agree a deal to divide the islands, with two being kept by each side, a stance Tokyo has rejected. Some Japanese politicians and officials have in the past also proposed some form of division of the disputed area, but any such compromise remains deeply controversial.